(A) Representative images of pancreatic sections from day 15 (D15) pregnant (D15) WT mice and quantitation expressed as average MafA fluorescence intensity of BrdU⁺ and BrdU^– populations (n = 5 mice/group). Individual cells are plotted in Supplemental Figure 6A. (B) Representative images of pancreatic sections from pregnant (D15) mice stained for BrdU as well as antibodies directed against insulin and Pdx1, Neurod1, or Ucn3 (n = 5 mice/group). (C) Representative images of pancreatic sections from virgin and pregnant (D15) TNR mice, with quantitation of percentage of GFP⁺ β cells (n = 4–5 mice/group). (D) Representative images of pancreatic sections from pregnant (D15) TNR mice showing Ki67, insulin, and GFP reporter staining (top), with increased magnification of the boxed region (bottom). Arrows indicate Ki67⁺ β cells. Quantitation of percentage of GFP⁺ β cells or percentage of GFP⁺Ki67⁺ β cells (n = 5 mice/group; overall count of 3995 total β cells and 188 Ki67⁺ β cells). (E) Quantitation of average MafA fluorescence intensity in GFP^– and GFP⁺ β cells from chow-fed TNR mice, normalized to average value in GFP^– cells (n = 5 mice). Approximately 1000 cells quantified per pancreas. Scale bars: 20 μm. All data are shown with group means. *P < 0.05; **P < 0.01; ***P < 0.001, 2-tailed t test.